Flame retardation of textiles

ABSTRACT

The present invention discloses a flame retardant formulation comprising tetrabromobisphenol A bis(2,3-dibromo-propyl ether) (FR-720) particles in a liquid carrier, wherein the particle size of at least 50% of said particles (d50) is smaller than about 50 microns. Furthermore, the present invention discloses a flammable textile fabric, coated by a flame retardant film comprising FR-720 particles which are substantially homogeneously dispersed in or on the flammable textile fabric, and further of a process of preparing these flame retardant formulations and of a process of applying these formulations onto a flammable textile fabric.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to the fieldof flame-retardants and, more particularly, but not exclusively, tonovel flame retardant formulations that form homogeneous flame retardantfilms on textiles, their preparation and flame-retarded textile fabricswhich comprise these films.

Textiles are an essential part of everyday life and are found, forexample, in draperies, cloths, furniture and vehicle upholsteries, toys,packaging material and many more applications. Consequently, textileflammability is a serious industrial concern.

Flame retardants used for the protection of textiles must beenvironmentally and physiologically safe, compatible with the fabric,non-damaging to the aesthetical and textural properties of the fabric(for example, to remain transparent) and must be resistant to extensivewashing and cleaning (generally termed as “durable”). Above all, a flameretardant agent suitable for textile treatment should pass the standardflammability tests in the field, preferably even after 5, 10 or 50washing cycles.

Flame retardation of textiles using aromatic bromine-containingformulations adhered to the substrates by means of binders, has beenlong established (for instance, U.S. Pat. No. 3,955,032 and U.S. Pat.No. 4,600,606).

The main drawbacks of existing formulations include high bromine contentdemand, high dry add-on demand, streak marks on dark fabrics, excessivedripping during combustion of thermoplastic fibers and dispersioninstability. Most of these drawbacks are inherent to the aromaticbromine compounds used. Furthermore, using existing aromatic brominecontaining formulations, the percentage resin component may be as highas 60-70% by weight of the total fabric weight (add-on), in order toobtain satisfactory flame retardation (see Toxicological Risks ofSelected Flame-Retardant Chemicals (2000), by Donald E. Gardner (Chair)Subcommittee on Flame-Retardant Chemicals, Committee on Toxicology,Board on Environmental Studies and Toxicology, National Research Councilpage 507). This high add-on is due in part to the large amount of binderneeded to fix the flame retardant (FR) agents to the textile. The bindermay be as high as 50% by weight of the total FR formulation (seeToxicological Risks of Selected Flame-Retardant Chemicals (2000) page507). Due to its substantial presence, the binder contributes toflammability and dripping, which requires more bromine content, thuscreating an inefficient cycle. Yet further, often, the high add-onadversely affects otherwise desirable aesthetical and texturalproperties of the fabric. For example, upon application of a FR with alarge amount of binder, fabrics may become stiff and harsh and may haveduller shades, and poor tear strength and abrasion properties.

Over the years, several antimony-based compounds have been used asflame-retardant synergists, including Sb₂O₃, Sb₂O₅ and Na₃SbO₄ (Touval,I., (1993) “Antimony and other inorganic Flame Retardants” in KirkOthmer's Encyclopedia of Chemical Technology, Vol. 10, p. 936-954,4^(th) Edition, John Wiley and Sons, N.Y.). Antimony based compounds arevery expensive and are therefore not used on their own, but are used assynergists with other flame retardants. The addition of antimony oxideto halogenated flame retardants increases their efficiency and reducesthe amount of additives and/or halogenated FR agent to be used. However,the addition of such synergist is costly and further contributes to thehigh add-on of the formulation.

Thickening agents are also often added to flame retardant formulationsin order to increase their viscosity and facilitate the application ofthe FR formulations on the textiles. However, as in the case of binders,the thickening agents are often flammable compounds themselves, andtherefore an additional amount of FR agent and/or synergist in necessaryto overcome this adverse effect.

Thus, order to obtain better flame retarded textiles, an efficient flameretardant, which can be useful in low binder/thickener content, andwhich would have good dispersion properties, on top of the otherqualities discussed above, is required.

It is important to note that although textiles may be resistant to openflame burning, the smoldering (also termed “after flame”), which maypersist after the open flame has been extinguished, can eventually leadto complete digestion of the fabric (see, for example, “ToxicologicalRisks of Selected Flame-Retardant Chemicals—2000”, Donald E. Gardner(Chair), Subcommittee on Flame-Retardant Chemicals, Committee onToxicology, Board on Environmental Studies and Toxicology, NationalResearch Council). Accordingly, in order to overcome the smolderingproblem in textiles, the addition of a smoldering suppressant (SS),which is also referred to herein, interchangeably, as a smolderingsuppressing agent, is frequently required.

WO 07/096,883, by the present inventors, discloses the preparation anduse of Aluminum Ammonium Super Phosphoric acid salt (AlASP) as a novelsmoldering suppressant agent that is highly beneficial for applicationonto textiles.

Tetrabromobisphenol-A bis(2,3-dibromopropyl ether) (FR-720) is a flameretardant that comprises a combination of aromatic and aliphatic bromineatoms, which provides high FR efficiency and good thermal stability.FR-720 is useful in many applications, especially, but not exclusively,in the field of flame retardation for plastic compositions. FR-720 isinsoluble in water and has a relatively low melting range (113-117° C.).The preparation of FR-720 is described, for example, in U.S. Pat. No.5,710,347.

WO 05/103361, by the present inventors, discloses flame retardantaqueous dispersions or suspensions comprising FR-720 for use in textile.The binder content in these formulations is between 30% and 40% byweight of the aqueous formulation.

SUMMARY OF THE INVENTION

It has now been found that FR-720 can be processed to obtain a novelflame retardant formulation, which can be applied on a variety offabrics while exhibiting unexpected homogeneity and transparency, at arelatively low binder content. This formulation forms a transparentflame retardant film on the textile fabric, the properties of which aremaintained after many washing cycles, and are further maintained evenwhen the whitish antimony-based FR synergist forms part of theformulation.

It has been further surprisingly found that the addition of AlASP to theflame retardant formulations described herein can result in a novelflame retardant and smoldering suppressant formulation, which forms aflame retardant and smoldering suppressant film comprising FR-720particles, such that the FR-720 particles are homogeneously dispersed inor on a variety of fabrics, at low binder and thickener contents, yetyielding a durability of at least 15 washing cycles.

Thus, according to an aspect of embodiments of the present inventionthere is provided a flame retardant formulation comprisingtetrabromobisphenol A bis(2,3-dibromopropyl ether) (FR-720) particles ina liquid carrier, wherein the particle size of at least 50% of theparticles (d₅₀) is smaller than about 50 microns.

According to some embodiments, the formulation further comprises adispersing agent.

According to some embodiments, the formulation further comprises abinding agent, wherein an amount of the binding agent is less than 25weight percentages of the total weight of the formulation. In someembodiments, this amount of ranges from 5 weight percentages to 20weight percentages of the total weight of the formulation.

According to some embodiments, the particle size of at least 90% of theparticles (d₉₀) is smaller than about 100 microns.

According to some embodiments, the particle size of at least 10% of theparticles (d₁₀) is smaller than about 10 microns.

According to some embodiments, the formulation is capable of forming atransparent film on a glass substrate.

According to some embodiments, the formulation further comprises asmoldering suppressant agent. In some embodiments, this smolderingsuppressant agent is an aluminum ammonium super phosphoric acid salt(AlASP). In some embodiments, the ratio between the smolderingsuppressing agent and the FR-720 particles ranges from about 1:5 and5:1, more preferably from about 1:1 and 1:3.

According to some embodiments, the formulation further comprises a flameretardant synergist.

In one embodiment, the formulation comprises AlASP and the synergist isantimony oxide (ATO). In this case, the molar ratio between theelemental antimony in the ATO and the elemental halogen in the FR-720 isless than 1:3.

According to some embodiments, the liquid carrier is an aqueous carrier.In some embodiments, the formulation is in a form of an aqueousdispersion. More preferably, the particles are homogeneously dispersedin the dispersion.

According to some embodiments, the formulation comprises FR-720 in anamount of between 5 weight percents to about 70 weight percents, anacrylic binder in an amount of between 5 weight percents to about 50weight percents, antimony oxide in an amount of up to about 40 weightpercents, and water. In some embodiments, the formulation furthercomprises AlASP in an amount of up to 70 weight percents.

According to some embodiments, the formulation is characterized by aviscosity that ranges from about 100 centipoises to about 2000centipoises.

According to another aspect of embodiments of the invention there isprovided a flammable textile fabric, being coated by a flame retardantfilm, wherein the film comprises tetrabromobisphenol Abis(2,3-dibromopropyl ether) (FR-720) particles which are substantiallyhomogeneously dispersed in or on the flammable textile fabric.

The phrase “flammable textile fabric”, as used in the context of thisaspect of embodiments of the invention, describes a flammable textilefabric that is coated by a FR film, and hence is also referred tohereinafter as “coated flammable textile fabric” or “treated flammabletextile fabric”.

According to some embodiments of the invention, the film is formed uponapplying any of the formulations described herein onto the fabric, andcuring the formulation.

According to some embodiments, the coated flammable textile fabric ischaracterized by at least one aesthetical or textural property which issubstantially the same as that of the flammable textile fabric per se.

According to some embodiments, the flammable textile fabric, as well asthe coated flammable textile fabric, is a colored textile fabric.

According to some embodiments, the flame retardant film coating theflammable textile fabric has a durability of at least 15 washing cycles.

According to some embodiments, the coated flammable textile fabricdescribed herein is characterized by a relative standard deviation (RSD)of average bromine content, as defined by a gridline-12-samples-test,which is smaller than 15%, wherein the average bromine content iscalculated upon cutting the fabric into twelve equal slices, eachweighing about 0.5 gram, separately measuring the bromine content ofeach slice, and calculating the RSD of the separate bromine contentvalues.

According to some embodiments, the coated flammable textile fabric ischaracterized by an after flame time, as defined by ASTM D-6413 12seconds ignition test, of less than 5 seconds.

According to some embodiments, the coated flammable textile fabric ischaracterized by an after glow time, as defined by ASTM D-6413 12seconds ignition test, of less than 150 seconds, preferably of less than50 seconds.

According to some embodiments, the coated flammable textile fabric ischaracterized by a char length, as defined by ASTM D-6413 12 secondsignition test, of less than 15 centimeters, preferably of less than 5centimeters.

According to yet another aspect of embodiments of the invention there isprovided a process of preparing the flame retardant formulationdescribed herein, the process comprising:

-   -   mixing tetrabromobisphenol A bis(2,3-dibromopropyl ether)        (FR-720) particles having a d₅₀ that is larger than 50 microns,        with an aqueous carrier,    -   and milling the dispersion until:    -   a) the particle size of at least 90% of the FR-720 particles        (d₉₀) is smaller than about 100 microns; and/or    -   b) the particle size of at least 50% of the FR-720 particles        (d₅₀) is smaller than about 50 microns; and/or    -   c) the particle size of at least 10% of the FR-720 particles        (d₁₀) is smaller than about 10 microns

According to some embodiments of the invention, the milling is conductedfor at least 10 minutes.

According to some embodiments, this process further comprises, eitherbefore or after the milling,

adding at least one additive selected from the group consisting of aflame retardant synergist, a smoldering suppressant agent, a surfaceactive agent, an antifoaming agent, a preservative, a stabilizing agent,a binding agent, a thickening agent, a wetting agent, a dispersingagent, a suspending agent, a pH buffer and any mixture thereof; andoptionally adding more liquid carrier.

According to still another aspect of embodiments of the invention thereis provided a process of applying the flame retardant formulationdescribed herein onto a flammable textile fabric, the processcomprising:

contacting the flammable textile fabric with the flame retardantformulation described herein, so as to obtain the flammable textilefabric having the flame retardant applied thereon; and

heating the flammable textile fabric having the flame retardant appliedthereon.

According to some embodiments of the invention, the heating is conductedat a temperature of between 140° C. and 180° C.

According to some embodiments, the contacting is effected by spreading,coating, padding, dipping, printing, foaming and/or spraying.

As used herein the term “about” refers to ±10%.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

The term “consisting of means “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

The word “exemplary” is used herein to mean “serving as an example,instance or illustration”. Any embodiment described as “exemplary” isnot necessarily to be construed as preferred or advantageous over otherembodiments and/or to exclude the incorporation of features from otherembodiments.

The words “optionally” or “alternatively” are used herein to mean “isprovided in some embodiments and not provided in other embodiments”. Anyparticular embodiment of the invention may include a plurality of“optional” features unless such features conflict.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

As used herein the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques and proceduresby practitioners of the chemical art.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIGS. 1A-B present plots showing the particle size distributions of aFR-720 dispersion before milling (as the volume percentage versusparticle size, FIG. 1A) and of a wet-milled dispersion (as the volumepercentage versus particle size, FIG. 1B), obtained by a MalvernMastersizer 2000G;

FIGS. 2A-F present comparative optical microscope micrograph images of afilm comprising FR-720, acrylic binder and Antimony Oxide (ATO, FIG.2A), FR-720 only (FIG. 2B), FR-720 and ATO (FIG. 2C), FR-720 and acrylicbinder (FIG. 2D), acrylic binder only (FIG. 2E) and of acrylic binderand ATO (FIG. 2F);

FIGS. 3A-B present scanning electron microscopy (SEM) images of apolyester fabric treated with a milled FR-720 formulation, according tosome embodiments of the invention (FIG. 3A), and an Energy DispersiveX-ray Spectra (EDS) of the surface displayed in FIG. 3A (FIG. 3B);

FIGS. 4A-C present SEM images of a polyester fabric treated with amilled FR-720 formulation (formulation no. 2A), after curing, at ×100magnification (FIG. 4A), at ×200 magnification (FIG. 4B) and at ×400magnification (FIG. 4C);

FIGS. 5A-C present SEM images of a polyester fabric treated with amilled FR-720/acrylic binder formulation (formulation no. 4A), beforecuring, at ×100 magnification (FIG. 5A), at ×200 magnification (FIG. 5B)and at ×400 magnification (FIG. 5C);

FIGS. 6A-D present SEM images of a polyester fabric treated with amilled FR-720/acrylic binder formulation (formulation no. 4A), aftercuring, at ×100 magnification (FIG. 6A), at ×200 magnification (FIG. 6B)and at ×400 magnification (FIG. 6C), further presenting a back-scatteredimage of FIG. 6B (FIG. 6D);

FIGS. 7A-C present scanning electron microscopy (SEM) images of apolyester fabric treated with a non-milled FR-720 formulation(formulation no. 2B) after curing, at ×100 magnification (FIG. 7A), at×200 magnification (FIG. 7B) and at ×400 magnification (FIG. 7C);

FIGS. 8A-C present SEM images of a polyester fabric treated with anon-milled FR-720/acrylic binder formulation (formulation no. 4B),before curing, at ×100 magnification (FIG. 8A), at ×200 magnification(FIG. 8B) and at ×400 magnification (FIG. 8C); and

FIGS. 9A-D present SEM images of a polyester fabric treated with anon-milled FR-720/acrylic binder formulation (formulation no. 4B), aftercuring, at ×100 magnification (FIG. 9A), at ×200 magnification (FIG. 9B)and at ×400 magnification (FIG. 9C), further presenting a back-scatteredimage of FIG. 9B (FIG. 9D).

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to the fieldof flame-retardants and, more particularly, but not exclusively, tonovel flame retardant formulations that form homogeneous flame retardantfilms on textiles, their preparation and flame-retarded textile fabricswhich comprise these films.

It has now been found by the inventors of the present invention thatFR-720 can be processed to obtain a novel flame retardant formulationcomprising FR-720 particles in a liquid carrier, wherein the particlesize of at least 50% of these particles (d₅₀) is smaller than about 50microns. This formulation has been successfully applied on a variety ofsubstrates using low binder content, and resulted in a transparent andhomogeneous film being formed in or on the treated substrates. A varietyof white as well as colored textile fabrics coated by this film werecharacterized by a high degree of coating homogeneity, a high brominecontent and a high transparency, while successfully passing the strict15-seconds-ignition textile flammability test and possessing adurability of at least 15 washing cycles.

Thus, according to one aspect of embodiments of the invention, there isprovided a flame retardant formulation comprising tetrabromobisphenol Abis(2,3-dibromopropyl ether) (FR-720) particles in a liquid carrier,wherein the particle size of at least 50% of these particles (d₅₀) issmaller than about 50 microns.

The phrase “particle size of at least 50% of the particles”, as usedherein, is interchangeably referred to herein and in the art as “d₅₀”and represents the particle size which 50% of the particles do notexceed. As is widely acceptable in the art, the term “size” representsthe particle radius of the particles of a given FR, and is typicallydetermined by conventional analytical techniques such as, for example,microscopic determination utilizing a scanning electron microscope or bymeans of a laser granulometer (such as a small angle scattering, forexample, a Malvern). The volumetric distribution of the sample relatesto the weight distribution. While the d₅₀ particle radius is derivedfrom a volumetric particle size or length and expresses the same values,this phrase is also referred to interchangeably herein and in the art as“volumetric average particle size”, “volumetric average particle length”and “average particle length”. Similarly, d₉₀ is defined as the particlesize which 90% of the particles do not exceed and d₁₀ is defined as theparticle size which 10% of the particles do not exceed.

In some embodiments, the formulation described herein is prepared bymilling a coarse dispersion of FR-720 particles. Exemplary millingtechniques suitable for use in the context of embodiments of theinvention are provided in detail below.

A coarse dispersion of FR-720 that can be transformed upon milling tothe formulation of the present invention is typically characterized byan upper “cut-off” of the particle size (largest particle size) which isabout 25,000 microns, preferably a cut-off ranging from about 1500microns to about 2500 microns and/or by a d₉₀ ranging from about 100microns to about 1000 microns and/or by a d₅₀ ranging from about 50microns to about 500 microns and/or by a d₁₀ ranging from about 10microns to about 100 microns. Such a FR-720 coarse dispersion isavailable by adding FR-720 in small portions to a liquid carrier,optionally adding a dispersing agent, and mixing for at least 10minutes.

The formulation described herein, obtainable by wet milling the FR-720coarse dispersion described above, is characterized by a “cut-off” ofthe particle size which is lower than 550 microns and by a d₅₀ which islower than 50 microns. Preferably, the d₅₀ ranges from about 5 micronsto about 30 microns, more preferably the d₅₀ ranges from about 8 micronsto about 25 microns.

Furthermore, the formulation described herein, obtainable by wet millingthe FR-720 coarse dispersion described above, is characterized by a d₉₀which is lower than 100 microns. Preferably, the d₉₀ ranges from about20 microns to about 80 microns, more preferably the d₉₀ ranges fromabout 30 microns to about 45 microns.

Furthermore, the formulation described herein, obtainable by wet millingthe FR-720 coarse dispersion described above, is characterized by a d₁₀which is lower than 10 microns. Preferably, the d₁₀ ranges from about 1micron to about 10 microns, more preferably the d₁₀ ranges from about1.5 microns to about 5 microns.

Indeed, as can be seen in the Examples section below, the milled FR-720dispersion was characterized to have a d₉₀ of 38-39 microns, a d₅₀ of12.6-14 microns and a d₁₀ of 2.6-3 microns.

Illustrative particle size distribution functions of the coarse FR-720starting material dispersion and of the formulation described herein canbe seen in FIGS. 1A and 1B, and in Tables 1 and 2, respectively.

According to an embodiment of the invention, the formulation describedherein further includes a dispersing agent (also termed hereininterchangeably as a “suspending agent” or “thickening agent”). The useof a dispersing agent contributes to the stability and homogeneity ofthe FR-720 formulation. The dispersing agent is most preferablyintroduced to the FR-720 coarse dispersion starting material before themilling step.

Examples of dispersing agents and/or suspending agents and/or thickeningagents that are suitable for use in the context of the presentembodiments include, but are not limited to, acrylic acids, acrylicacids ester copolymer neutralized sodium polycarboxyl such asnaphthalene sulfonic acid-formaldehyde condensate sodium salt,alginates, cellulose derivatives and xanthan.

If present, the dispersing agent is added in an amount ranging from 0.5weight percentages to 5 weight percentages of the total weight of theformulation.

Preferably, the dispersing agent is selected from the group consistingof Dispergator WA, AMP-95, Clorocontin NGD and Triton X-100®. Furtherpreferably, the dispersing agent is a nonionic surface active agent,such as Triton X100®.

According to some embodiments of the invention, the formulationdescribed herein further includes a binding agent (also termed hereininterchangeably as a “binder”). The use of a binder contributes to theadherence of the molecules of a flame retardant, herein the FR-720, tothe substrate, herein the textile fabric.

As discussed in detail hereinabove, brominated FRs are known astypically requiring a large amount of a binder to affix them to thetextile substrate, which may typically reach about 50% by weight of thetotal FR formulation [Mischutin (1978) supra]. Such a large amount of abinder results in high add-on, which, as is further discussed in detailhereinabove, is undesirable since it causes a deterioration of thetextile properties, for example, resulting in a stiffening of thefabrics or fading of their shades, and may further lower the tearstrength and abrasion properties of the fabric. Unfortunately, the highbinder content also contributes in itself to flammability and dripping.

It has now been uncovered by the present inventors that the formulationdescribed herein can be effectively applied on various substrates in thepresence of relatively low concentrations of a binder.

While the exact amount of binder used depends on the flame retardant'sconcentration, as well as on the fabric type onto which the formulationis to be applied, it has been shown that in the case of various textilesubstrates, the concentration of the binding agent in the formulationsdescribed herein can be lower than 25 weight percents of the totalweight of the formulation, and even lower than 20 weight percents of thetotal weight of the formulation. As is demonstrated in the Examplessection that follows, it was found that milled FR-720 formulationscontaining 15 weight percents of a binder were well adhered to thesubstrates, and remained such even upon subjecting the substrate to asmuch as 15 washing cycles, while maintaining the flame resistanceproperties. Thus, for example, it has been demonstrated that a cottonfabric having a milled FR-720 formulation that contains 15% by weight ofa binder applied thereon, passed a 12 seconds ignition test (ASTM D6413) with an after flame time of 2 seconds, an after glow time of 113seconds, and a char length of 4.5 centimeters, even after 15 cycles ofwashing (see, Example 11). In another example, it has been demonstratedthat a cotton fabric having a milled FR-720/ammonium phosphateformulation that contains 15% by weight of a binder applied thereon,passed a 12 seconds ignition test (ASTM D 6413) with an after flame timeof 0 seconds, an after glow time of 33 seconds, and a char length of14.5 centimeters, even after 15 cycles of washing (see, Example 12).

Thus, according to some embodiments, the concentration of the binder isless than 25% by weight, and preferably ranges from 5 % to 20% byweight.

The binder used in the formulations described herein is chosen to becompatible with the flame retardants and the additional additives in theformulation and depending on the specific application.

Preferably, when the formulations described herein are applied ontextiles, the binder selected is suitable for use on textiles, and istherefore selected to be both non-damaging to the aesthetical andtextural properties of the fabric, and durable (to washing, drying, UVlight etc.).

Representative examples of binders that are suitable for use on textilesinclude, without limitation, acrylates, polyurethanes, and PVC.Preferably, the binder used in the formulations described herein is anacrylate.

Examples of acrylates that are suitable for use as binders in thecontext of the present invention include, but are not limited to,2-phenoxyethylacrylate, propoxylated 2 neopentyl glycol diacrylate,polyethylene glycol diacrylate, pentaerythritol triacrylate,2-(2-ethoxyethoxy) ethyl acrylate, butyl acrylate, styrene, and others.

It is noted that the present inventors have now also successfullyprepared stable formulations containing no binder at all. For example,Example 5 in the Examples section that follows, presents a formulationof milled FR-720 only (formulation 2A) and a formulation of milledFR-720 and ATO (formulation 3) only. The film prepared of FR-720 only(film no. 2A) appeared to be transparent and uniform, as can be seen inFIG. 2B and had a very low turbidity (9.41 NTU, Table 6, Example 8).Furthermore, a fiber coated by formulation 2A appeared to be veryhomogenously, smoothly and completely coated by the fibers. In addition,the flame retardant particles were observed even deep in the yarn core.As seen in FIGS. 4A-C, no significant clumps or inter yarn adhesionswere observed.

Thus, according to an alternative embodiment of the present invention,the formulations of the present invention are free of a binder.

As shown in the Examples section hereinbelow, the milled FR-720particles of the present embodiments were homogeneously dispersed, withor without the acrylic binder, in the dispersion, thereby rendering thefilm formed thereof to be transparent, as shown in FIGS. 2A-F for thefilms described in Example 8 hereinbelow.

Thus, according to a preferred embodiment of the invention, there isprovided a formulation of the FR-720 particles described hereinabovecapable of forming a transparent film on a substrate.

As used herein, the term “transparent” or “transparency” shall bedistinguished from the term “translucent” or “translucency.” Atransparent material is characterized by its ability to convey imagestherethrough. A translucent material conducts light, but does not permitviewing of images therethrough.

The term “film” as used herein refers to a coating having a thicknesswhich is substantially thinner compared to the thickness of thesubstrate which is coated by this film. The thickness of the coating ispreferably, though not necessarily, essentially uniform over the surfaceof the substrate. The use of the term “film” includes not only films,but sheets as well. The thickness of the coating can assume any value,with the only possible limitations being those present from processinglimitations.

The FR formulation described herein therefore enables to maintain thevisual properties of the substrate on which it is applied. It has indeedbeen shown in the Examples section which follows, that a film formed byapplying a thin coating of the formulations of the present invention, ishighly transparent and has a low turbidity value. For example, the filmprepared of FR-720 only (film no. 2A in Table 7) was highly transparentand had a low turbidity of less than 10 NTU (1.37 NTU). Furthermore,microscopic image analysis also indicated that this film was transparentand uniform (FIG. 2B).

The transparent features of embodiments of the invention minimize oreliminate the visibility of the coating or film applied on the treatedsubstrate. This may be particularly significant in flame retardation ofcolored fabrics. As shown in the examples section which follows, themilled FR-720 formulations presented herein were successfully applied ona variety of colored fabrics (see, for example, Examples 13-15).Therefore, the FR-720 formulations presented herein can be used to coatfabrics even in highly visible applications, such as in the coating ofcloths, and even in the coating of dark colored cloths. Furthermore,given the improved qualities of the milled FR-720 formulations presentedherein, the processing of these formulations is easier and lessdetrimental to the industrial equipment due to the formation of highlydispersed formulations.

The flame retardant film presented herein is especially suitable forapplication to textiles, since it is has flame-retardant properties, istransparent, relatively flexible and essentially evenly spread on avariety of fabrics. Furthermore, these properties are maintained evenafter many washing cycles (at least 15 cycles).

The ability of the formulations presented herein to form transparentfilms can be conveniently determined either visually or with the aid ofa microscope. For example, the formulations were applied upon a glasssubstrate, such as on a glass microscope slide, or on a glassturbidimeter bottles, as can be seen in FIGS. 2A-2F. FIG. 2B depicts themilled FR-720 formulation and shows a transparent molten film. Thetransparency of this film on glass can then be correlated to thehomogeneity of the film or coating of the same formulation on a textilefabric and thus, the properties of these films are indicative of theeffect of the formulations of the present embodiments on othersubstrates, such as fabric.

Indeed, SEM pictures showing the fabrics treated by milled FR-720formulations versus by formulations of non-milled FR-720, showedconsiderable differences. Thus, for example, FIGS. 7A-C (Example 10)depict a polyester fabric sample treated and cured by a formulationcontaining only a dispersion of a non-milled FR-720 particles(formulation 2B in Table 4 below) and show the existence of non-meltedFR-720 particles as well as the formation of FR-720 agglomerates betweenthe fibers. Furthermore, the melt was non-uniform, did not evenly coverthe fibers and inter yarn adhesions were observed. In contrast, in aparallel sample formed of a formulation comprising milled FR-720particles (formulation 2A in Table 4 below), the coating appeared as avery homogenously FR-720 melt spread on the fabric, which smoothly andcompletely coated the fibers and was observed even deep in the yarncore. No significant clumps or inter yarn adhesions were observed (FIGS.4A-C, Example 9).

The term “yarn”, as used herein, refers to a strand or a bundle oftextile fibers.

Thus, according to embodiments of the invention, the formulationdescribed herein is capable of forming a transparent film on a glasssubstrate.

In each of the formulations described herein, the amount of the flameretardant can range from about 1 weight percent to about 70 weightpercents of the total weight of the formulation. Preferably, the amountof the FR-720 flame retardant ranges from about 5 weight percents toabout 70 weight percents, depending on the required bromine content onthe fabric. More preferably, this amount ranges from about 5 weightpercents to about 50 weight percents, and in the presently mostpreferred composition that amount of the FR-720 is about 5-30 weightpercents of the total weight of the composition.

In addition to the milled FR-720 as a flame retardant, the liquidcarrier and optionally the dispersing agent and/or the binder, theformulations described herein may further comprise additionalingredients which may improve the performance of the formulation. Thus,in one embodiment, the milled FR-720 formulations can further compriseone or more of additional flame retardants, flame retardant synergistsand smoldering suppressants.

As used hereinafter the term “smoldering”, also known in the art as“after flame burning” or “after glow” refers to a burning whichcontinues after the open flame has been extinguished. The phrase“smoldering suppressant”, which is also referred to hereininterchangeably as “smoldering suppressing agent” or “SS”, thereforedescribes a compound or a composition which reduces or eliminates thetendency of a substance to burn after no longer being exposed to aflame.

Some of the presently known flame retardants may also exert smolderingsuppression and are therefore further referred to as smolderingsuppressants.

Formulations containing flame retardants and smoldering suppressantsand/or flame retardants which are also smoldering suppressants can serveas flame retardant and smoldering suppressing formulations.

The flame retardants and smoldering suppressants added to theformulations described herein can be either halogenated flame retardantsor non-halogenated flame retardants. Preferably, in cases where the FRformulation is intended to be applied on a textile fabric, the addedflame retardants and smoldering suppressants are selected suitable foruse on textiles.

Any flame retardants and smoldering suppressants can be used along withthe milled FR-720 formulations presented herein, as long as uponapplication thereof, the coating shall remain homogeneous and/ortransparent as required.

Examples of suitable smoldering suppressants include, but are notlimited to urea, melamine and phosphate salts. In one embodiment, thesmoldering suppressant is an ammonium phosphate.

The phrase “ammonium phosphate” refers to an ammonium salt of aphosphate, whereby the phosphate can be a monophosphate, a diphosphateor a polyphosphate. Preferably, the phosphate is a polyphosphate. Mostpreferably, the polyphosphate is a superpolyphosphate, such as aluminumammonium super phosphate (AlASP).

As shown in the Examples section which follows, adding up to 70 weightpercents of AlASP, but as low as 1 weight percent of AlASP wassufficient to decrease the “after-glow” of the treated fabric in asatisfactory extent (see, Examples 6 and 12).

According to some embodiments, the ratio between the smolderingsuppressing agent and the FR-720 ranges from about 1:5 and 5:1. In someembodiments, this ratio ranges from about 1:1 to about 1:3.

In addition to the milled FR-720, the liquid carrier and optionally thebinder, the dispersing agent or any of the other additives mentionedhereinabove, the formulations described herein may further compriseadditional ingredients which may improve the flame retardancyperformance of the formulation. An exemplary ingredient is a flameretardant synergist, which acts in synergy with the milled FR-720 andthus enhances the flame resistance properties of the formulation.

Thus, according to some embodiments, the formulation described hereinfurther comprises at least one fire retardant synergist. An exemplaryfire retardant synergist which is suitable for use in this context ofthe present invention is antimony oxide (ATO), being, for example Sb₂O₃and/or Sb₂O₅.

As is detailed in the Background section hereinabove, when a FRformulation is applied on textiles, large amounts of ATO are undesirabledue to cost, toxicity, color, environmental concerns and increase in thetotal add-on. Hence, lower amounts of a FR synergist, as compared to thepresently known FR formulations, are required so as to maintainefficient flame retardancy, washing fastness and desirable fabricproperties.

It has now been shown that the molar ratio between the fire retardantsynergist and FR-720 can range from about 1:1 to about 1:10, and evenfrom about 1:3 to about 1:6. Thus, the need to use large amounts of a FRsynergist such as ATO is circumvented due to the relatively enhancedbinding of the milled FR-720 to the substrate, and thus the resultingrelatively high FR content on the substrate (over 17% of bromine onfabric, compared to about 10% in the non-milled formulation).

In particular, it has been shown that by using AlASP as a smolderingsuppressant, in admixture with the milled FR-720 of the presentembodiments, the amount of synergist can be further lowered, from abromine:antimony ratio of 1:3 (as in Table 3) to a ratio of about 1:6(as in Table 5), without adversely affecting the flame resistance of theformulation. This of course is most advantageous due to the high cost ofthe ATO.

Thus, according to some embodiments, the molar ratio between the flameretardant synergist and the FR-720 flame retardant in the formulationsdescribed herein ranges from about 1:1 to about 1:6 of the active atomsin each compound (antimony and the halogen, respectively).

Furthermore, according to other embodiments of the invention, when theformulation comprises AlASP and the synergist is antimony oxide (ATO),the molar ratio between the elemental antimony in the ATO and theelemental halogen in the FR-720 is less than 1:3.

The milled FR-720 formulations described herein can further compriseadditional ingredients that may stabilize the formulation, prolong itsshelf-life and/or provide it with other desired properties such ascertain viscosity, homogeneity, and adherence to the substrate.

Thus, according to some embodiments, the formulation may yet furthercomprise one or more of such additional ingredients. These include, forexample, surface active agents, wetting agents, suspending agents,antifoaming agents, defoaming agents, preservatives, stabilizing agents,a pH buffer, binding agents, thickening agents and any mixture thereof.

Preferably, these additives are used in an amount of up to 10 weightpercents of the total weight of the formulation.

The surface active agents and/or wetting agents can be nonionic and/orionic (cationic or anionic) agents.

Examples of nonionic surface active and/or wetting agents that aresuitable for use in the context of the present invention include, butare not limited to, polyoxyethylene (POE) alkyl ethers, preferably NP-6(Nonylphenol ethoxylate, 6 ethyleneoxide units) such as DisperByk®101.

Examples of anionic surface active and/or wetting agents that aresuitable for use in the context of the present invention include, butare not limited to, free acids or organic phosphate esters or thedioctyl ester of sodium sulfosuccinic acid.

Preferred formulations, according to some embodiments of the invention,comprise FR-720 in an amount of between 5 weight percents to about 70weight percents, an acrylic binder in an amount between 5 weightpercents to about 50 weight percents, antimony oxide in an amount ofbetween 0 weight percent to about 40 weight percents, and water.

Furthermore, preferred formulations according to embodiments of theinvention further comprise AlASP in an amount of up to about 70 weightpercents.

As demonstrated in the Examples section which follows, milled FR-720dispersions were found to be more viscous than non-milled FR-720dispersions having the same FR concentration (amount), due to the largersurface area of the particles, facilitating further processing of thesecompositions.

Hence, preferred compositions according to some embodiments of theinvention are characterized by a viscosity that ranges from about 100centipoises to about 2,000 centipoises. As is demonstrated in theExamples section that follows, exemplary compositions were shown to havea viscosity in the range of from about 200 centipoises to about 1,700centipoises. Compositions characterized by such a viscosity are highlyadvantageous since the relatively high viscosity circumvents the need touse large amounts of thickening agents when applying a formulation thatcontains the FR composition to substrates. As discussed hereinabove,large amounts of thickening agents, which are often required so as toefficiently apply low-viscosity FR formulations onto textiles, arehighly disadvantageous due to their contribution to the generalflammability of the substrate.

It was now surprisingly found that the addition of AlASP (Example 6),which is a smoldering suppressant agent, was useful also as a thickeningagent, thus circumventing the need to add large amounts of polymeric ororganic thickening agent. Typical increase in viscosity observed withaddition of AlASP ranged from none to 5000 cps, depending onconcentration. This effect obviates the need to add up to 5 weightpercent thickener to the formulations.

Examples of defoaming and/or antifoaming agents that are suitable foruse in the context of the present invention, include, but are notlimited to, mineral oil emulsions, natural oil emulsions, and preferablyare silicon oil emulsions, such as AF-52™

Examples of preserving or stabilizing agents that are suitable for usein the context of the present invention, include, but are not limitedto, formaldehyde and alkyl hydroxy benzoates; preferably the preservingor stabilizing agents is a mixture of methyl and propyl hydroxybenzoates.

Additionally, a salt (e.g., ammonium phosphate or a borate) or an oxide(e.g., sodium silicate, alumina oxide, alumina oxide, aluminum hydrate)and any mixture thereof, may be added to the formulations of the presentinvention.

The term “carrier”, as used herein, refers to a liquid carrier anddescribes an inert material with which the composition is mixed orformulated to facilitate its application, or its storage, transportand/or handling. The liquid carrier can be, for example, an organicliquid carrier (e.g., alcohols, ketones, petroleum fractions, aromaticor paraffinic hydrocarbons, chlorinated hydrocarbons, or liquefiedgases) or an aqueous carrier.

Since the flame retardant formulations described herein are particularlyuseful for the treatment of textiles, the liquid carrier is preferably atextile acceptable liquid carrier, which is an inert, preferablyenvironmentally acceptable liquid carrier that is not harmful to thetextile. Preferably, the liquid carrier is an aqueous carrier and morepreferably the carrier is water.

The present inventors have now uncovered that an efficient applicationof FR-720-containing FR formulations, as presented herein, can beperformed while utilizing an aqueous dispersion of milled FR-720. As isdemonstrated in the Examples section that follows, formulationscontaining an aqueous dispersion of milled FR-720, either alone or incombination with flame retardant synergists or smoldering suppressantagents, are stable even during long-term shelving.

Thus, according to some embodiments of the invention, in each of theformulations described herein, the FR-720 is utilized in a form of adispersion, which comprises FR-720 particles dispersed in the liquidcarrier, wherein at least 50% of these particles have a particle sizewhich is smaller than about 50 microns. Preferably, the dispersioncomprises FR-720 particles such that at least 50% of these particleshave a particle size ranging from about 5 microns to about 30 microns,more preferably ranging from about 8 microns to about 25 microns.

These dispersions are characterized by a homogeneous dispersion of theparticles, as can be later manifested in the homogeneity of the bromineparticles in the treated fabric. As can be seen in the Examples sectionwhich follows, a textile fabric coated by the milled FR-720 particles,according to some embodiments of the invention, has a high brominecontent (>15%) and a low relative standard deviation of this value(lower than 15%), averaged over twelve separate and equal fabricspecimens.

Thus, according to some embodiments of the invention there is provided adispersion in which the particles of FR-720 are homogeneously dispersed.

While as described hereinabove, a preferred liquid carrier according tosome embodiments is an aqueous carrier and more preferably it is water,preferred formulations include an aqueous dispersion of milled FR-720.

Thus, according to another aspect of embodiments of the invention thereis provided a process of preparing flame retardant formulations, whichcomprise an aqueous dispersion of FR-720. The process, according tothese embodiments, is effected by providing and mixing a dispersioncontaining FR-720 coarse particles, namely particles having a d₅₀ whichis larger than 50 microns, and even larger than 100 microns or 200microns, and an aqueous carrier. Optionally, a thickening agent and/or adispersing agent can be added at this stage. Any commonly usedthickening agents and dispersing agents may be used. An exemplarythickening agent which was efficiently utilized in the preparation ofFR-720 dispersions is carboxymethylcellulose (see, for example, Example1 in the Examples section that follows); the mixed dispersion is thenmilled, to thereby obtain FR-720 particles dispersed in the solvent,such that the particle size of at least 50% of said particles (d₅₀) issmaller than about 50 microns.

Wet milling is defined as a milling step which is carried out in thepresence of a liquid and can be conducted according to any of the knownwet milling practices.

In particular, wet milling techniques comprise subjecting a liquidsuspension of coarse particles to mechanical means, such as a dispersionmill, for reducing the size of the particle size. One example of adispersion mill is a media mill, such as a bead mill. Wet bead millinginvolves preparing a suspension of pre-milled coarse particles. Thisdispersion is then drawn through a mill chamber containing a motordriven paddle and a quantity of grinding beads, to produce a finelymilled suspension. A screen is used to retain the beads within the millchamber whilst allowing the passage of product out of each mill chamber.Inline mixers may be used in the process line to break upmilled/pre-milled agglomerates.

The mills used for wet milling commonly employ toughened ceramic,stainless steel or tungsten carbide to form the mill chambers andagitating paddles. Commonly used grinding media include zirconium oxidebeads, which have a hardness approaching that of diamonds, orconsiderably softer grinding media based on polystyrene or other similarpolymers.

Other wet milling methods, besides bead milling, include using rollmills, pearl mills, vibro-energy milling, high pressure water jets,ultrasonics and orifice extrusion methods

It has been found that by using wet-milling, the disadvantagesassociated with dry milling FR-720 particles can be overcome, byavoiding, for example, undesired, melting of particles and/or formationof agglomerates, which may occur during dry milling due to therelatively low melting temperature of the FR-720 (113-117° C.).

In some embodiments, wet milling is performed in liquid media which donot dissolve the FR-720 particles and which are non-flammable. SinceFR-720 does not dissolve in water, it is preferable to conduct the wetmilling in the presence of water.

Milling media bodies useful for milling include balls, cylinders andother shapes of steel, corundum, porcelain, steatite, alumina, mixedoxides and quartz such as those having a diameter of from 0.05 to 20 mm.It has been found to be preferable to use a large number of fine millingballs, rather than fewer heavy balls. The finer balls perform a moreefficient co-milling action. Preferably the balls have a diameter of 2mm or less, and even 1.5 mm or less, under laboratory conditions. Largermilling balls may be required under industrial conditions.

Milling temperatures can be controlled for optimum performance of themedia mill and brittleness of the milled solid and milling media, whichcan become more elastic and resistant to particle size reduction athigher temperatures. Milling temperatures can range from as low asliquid air, liquid nitrogen or liquid argon temperatures, but are morecommonly from about −80° C. to about 50° C., well below the meltingtemperature of the FR-720 particles being milled.

Milling is conducted under atmospheric pressure in laboratoryconditions, but can be conducted under higher pressure in industrialconditions.

Preferably, the milling, under laboratory conditions, is conducted in a0.6 liter continuous mill at a rate of 3-4 kg/hour, but higher rates arepossible under industrial conditions, so as to achieve the desiredFR-720 particle size distribution.

The milling time is determined such that the main dispersion propertiesare obtained. In other words, milling is conducted until the particlesize of at least 90% of said FR-720 particles (d₉₀) is smaller thanabout 100 microns and/or until the particle size of at least 50% of saidFR-720 particles (d₅₀) is smaller than about 50 microns and/or until theparticle size of at least 10% of said FR-720 particles (d₁₀) is smallerthan about 10 microns. Hence, the milling time is from about 10 minutesto about an hour under laboratory conditions. Longer milling time ispossible but not required.

As is demonstrated in the Examples section that follows (see, forexample, Example 1), when milling was conducted during such a timeperiod, formulations comprising FR-720 particles having the desired d₅₀of less than 50 microns, as well as a desired, relatively narrow,particles size distribution, were obtained. For example, comparing theparticles size distribution before and after the milling of FR-720particles (see, for example, FIG. 1A and Table 1, versus FIG. 1B andTable 2, respectively), shows that after milling, the size distributionis narrower and has a higher ratio of micron-sized particles: the“cut-off” of the particle size was lowered from about 2100 micronsbefore milling to less than 550 microns, and even 470 microns aftermilling; the d₉₀ was lowered from above 100 microns, to a d₉₀ which isbelow 100 microns, preferably between about 20 microns to about 80microns, even more preferably between about 30 microns to about 45microns; the d₅₀ was lowered from above 50 microns to well below 50microns, preferably between about 5 microns to about 30 microns, evenmore preferably between about 8 microns to about 25 microns; Similarly,the d₁₀ was lowered from above 10 microns, to a d₁₀ which is below 10microns, preferably between about 1 micron to about 10 microns, evenmore preferably between about 1.5 microns to about 5 microns.

Without being bound to a specific theory, it is thought that achieving aparticle size which is smaller or equal to the average diameter of thefibers of the flammable fabric, positively affects the FR finishtransparency and smoothness.

The obtained milled dispersion was smooth and uniform and formed an easyto apply and/or process milling base, which is also termed hereinafter a“concentrate”. The concentrate, containing about 40% solids, wasnon-gritty and had the FR homogeneously dispersed within, and maintainedstable for about 1 day before phase separation occurred. The stabilitywas increased by adding suitable stabilizers, dispersants and/orthickeners, as detailed hereinbelow.

This milling base or “concentrate” is convenient to use and can be sold“as is” to the end-user, who can then create the final formulation,according to his/her exact needs, just before using the product.Furthermore, the amount of solids in the concentrate can be modified,based on the required properties of the product (for example, a requiredviscosity), by decantation (under laboratory conditions) and/or bycontrolling the solvent amount in the pre-milled dispersion. Forexample, the formulation shown in Table 3 had 37.7% solids, while theformulation of Table 4 (No. 1 therein) had as much as 58% solids.

Alternatively, additional components are added by the manufacturer suchthat the obtained complete formulation is the final product, rather thanthe concentrate. For example, as shows Example 3 hereinbelow, the FR-720concentrate, prepared according to Example 1, was redispersed in wateradding additional components, such as ATO, binder and dispersants, andthe resultant formulation passed the flammability tests (see Example 11)and evenly coated the fabric (as shown in FIGS. 3A-B).

According to another embodiment of the process according to this aspectof the present invention, prior to or subsequent to the milling, thereis added to the dispersion at least one ingredient selected from thegroup consisting of a flame retardant synergist, a smolderingsuppressant agent, a surface active agent, an antifoaming agent, apreservative, a stabilizing agent, a binding agent, a thickening agent,a wetting agent, a dispersing agent, a suspending agent, a pH buffer andany mixture thereof, as described hereinabove. It may be necessary atthis stage to add more of the aqueous carrier/solvent.

These formulations can be efficiently used when applied on textiles,avoiding the need to use excessive amounts of the flame retardant,binders, synergists and other additives. Furthermore, these formulationsare easily applied onto the textile substrate, while circumventing theneed to use drastic conditions as in the methods for incorporating flameretardants in the melt (i.e. at high temperatures and under pressure,for example by extrusion or injection molding).

Thus, according to another aspect of embodiments of the invention thereis provided a process of applying any of the flame retardantformulations described herein, to a substrate, preferably to a flammabletextile fabric. The process, according to these embodiments, is effectedby simply contacting the substrate with the flame retardant formulation,whereby the contacting can be effected by any industrially acceptablemanner. Subsequent to contacting the FR formulation, the substrate isheated to a temperature of from 140° C. to 180° C., preferably at about160° C., whereby the temperature is dictated by the melting temperatureof the FR-720 (113-117° C.) and by the curing temperature of the binder.The curing temperature is also related to the curing time and thetreated substrate. Thus, for example, curing the present formulations ona glass substrate necessitated more time than on textiles at the sametemperature (at 160° C., 15 minutes on glass compared to 4-6 minutes onfabric).

The industrially acceptable manner in which the contacting is effectedincludes, for example, spreading, coating, padding, dipping, printing,foaming and/or spraying the FR formulation onto the substrate. Paddingis a process that is typically used for applying the formulation on atextile substrate and is defined as a process in which the fabric isfirst passed through a padder containing the FR formulation, and is thensqueezed between heavy rollers to remove any excess formulation. Theprocess described herein can be effected, for example, either during thedying or the finishing stages of the substrate manufacture.

As is demonstrated in the Examples section that follows, theformulations and processes described herein were practiced so as toprovide substrates having the milled FR-720 formulations appliedthereon.

Hence, according to a further aspect of embodiments of the inventionthere is provided an article-of-manufacture which comprises a flammablesubstrate and any of the flame retardant formulations described herein,being applied thereon.

As used herein, the term “substrate” describes an article which has asurface that can be beneficially coated (either wholly or partially)with a flame retardant formulation. Exemplary articles include, withoutlimitation, textiles, wood, furniture, toys, bricks, electricalappliances, electrical cables, plastics and more.

Preferred substrates onto which the flame retardant formulationsdescribed herein can be beneficially applied are textile fabrics. Thetextile fabrics can be synthetic, natural or a blend thereof.Non-limiting examples of textile fabrics that can be beneficially usedin the context of the present invention include wool, silk, cotton,linen, hemp, ramie, jute, acetate fabric, acrylic fabric, latex, nylon,polyester, rayon, viscose, spandex, metallic composite, carbon orcarbonized composite, and any combination thereof. Representativeexamples of textile fabrics which were shown to be suitable for use inthe context of the present invention include, without limitation,cotton, polyester, acrylic fabric and combinations thereof.

The textile fabrics of this invention may be used as a single layer oras part of a multi-layer protective garment.

A textile substrate may be incorporated in various products, where it isdesired to reduce the substrate flammability. Such products include, forexample, draperies, garments, linen, mattresses, carpets, tents,sleeping bags, toys, decorative fabrics, upholsteries, wall fabrics, andtechnical textiles.

It is noted that a large variance of the bromine content in or on thesubstrate is common in treated textiles and results in an unevencoating. For example, the side of the fabric may have different amountsof the FR compared to the interior parts of the fabric, andoccasionally, parts of the fabric may have no coating at all or a verythin coating, compared to other parts thereof. Such an unevendistribution of the FR may mean that larger amounts of flame retardanthave to be used, in order to ensure the covering of the entire substrateand obtaining the required flame resistance, at a cost of a furtherincrease in the add-on and a decrease in the textural and/or aestheticalproperties of the substrate.

However, as shown in the Examples section which follows, it has now beenfound that a flammable textile fabric coated by a film comprising themilled FR-720 particles as presented herein is homogeneous, for examplein its bromine content, as is highly advantageous in terms of fabricuniformity, fabric appearance and fabric feeling.

Thus, according to another aspect of embodiments of the invention, thereis provided a flammable textile fabric coated by a flame retardant film,wherein this film comprises tetrabromobisphenol A bis(2,3-dibromopropylether) (FR-720) particles which are substantially homogeneouslydispersed in or on the fabric.

The flame retardant film is defined in detail hereinabove, and is formedupon applying any of the formulations described herein onto the fabric,and curing the formulation, as described hereinabove.

The phrase “substantially homogeneously dispersed in or on the fabric”describes a fabric having an even distribution of bromine particlestherein or thereon. This even distribution is reflected by the variancein the bromine content in different parts of the fabric.

The bromine content on the fabric can be measured by numerous methods,for example, by extracting the brominated FR from the fabric and thentitrating it with AgNO₃. Other methods include using an oxygen bomb,X-ray fluorescence and flame ionization chromatography.

Regardless of the specific method to determine the bromine content, inorder to also determine the variance or gradient in bromineconcentration throughout the fabric, it is necessary to conduct thesemeasurements in a carefully planned manner, so as to obtainrepresentative results of bromine content from different parts of thefabric. For example, a gridline-12-samples-test, as defined in themethods section hereinbelow, can be used such that the tested fabric iscut into twelve equal slices each weighing about 0.5 gram, the brominecontent of each slice is separately measured and the average of thesetwelve separate slices is calculated.

The relative standard deviation (RSD) of average bromine content canthen be a measure of the homogeneity of the coating on the fabric. Ithas been demonstrated herein that the RSD of the bromine content,measured using the gridline-12-samples-test, as described herein, waslowered from about 20% for the fabric treated by a non-milledformulation, to about 11.5% for the fabric treated by the milledformulation presented herein (see, Examples 9 and 10), a decrease ofover 40% in the RSD.

Thus, according to some embodiments of the invention, the flammabletextile fabric having applied thereon the formulation presented hereinin a form of a flame retardant film, is characterized by a relativestandard deviation (RSD) of average bromine content, which is smallerthan 15%.

These results are also consistent with the SEM/EDS pictures of apolyester fabric treated with the milled FR-720 aqueous formulation,prepared as described in Example 3. For example, FIG. 3A shows the evendistribution of bromine on the fibers as evenly-spread dots on the fibersurface.

Furthermore, it has now been shown that the milled FR-720 particles arenot only homogeneously dispersed in or on the fabric, but also thattheir total concentration on the fabric can be higher compared to asimilar fabric coated by a similar formulation comprising non-milledFR-720 particles.

For example, a fabric treated by a milled FR-720 formulation was foundto contain over 17% of bromine incorporated therein, compared to onlyabout 7% of bromine in a fabric treated by the non-milled formulation, a140% increase in bromine content. It is important to note that while theinitial bromine content in the formulations was similar in the milledand non-milled formulations (15.9% bromine before milling, compared to11.8-12.6% bromine in Tables 3 and 5 below), the high bromine content inthe final treated fabric reflects the better penetration of the FR-720particles of the present embodiments, into the fabric, and is a uniquecharacteristic of the formulations and articles presented herein.

This enhanced penetration, complemented by an enhanced homogeneousdispersion of FR-720 particles within the fabric, as describedhereinabove, can also be observed in the SEM pictures of fabrics coatedby the milled versus non-milled formulations. For example, as shown inExample 10 and FIGS. 7A-C, SEM pictures of a polyester fabric treated bythe non-milled FR-720 formulation clearly showed a melt of big particlesthat has formed a brittle film between the fibers, many FR-720 particlesthat have not melted and the melt itself appeared to be non-uniform anddid not evenly cover the fibers. Visually, the overall effect of thisnon-milled formulation is a translucent, rather than a transparent,coating. In contrast, as shown in Example 10, SEM pictures of apolyester fabric treated by the milled FR-720 formulation showed theeven distribution of bromine on the fibers (FIGS. 3A-B), and furthershowed the molten FR-720 particles spread very homogenously on thefabric, completely coating the fibers, deep into the yarn core, with nosignificant clumps or inter yarn adhesions being observed (FIGS. 4A-C).

It is beneficial that the increased homogeneity, durability and flameresistance in the final treated fabric were obtained even though theamount of binder is as low as 15% in the milled formulations, comparedto over 30% in presently known non-milled formulations of FR-720 (asdescribed, for example, in WO 05/103361).

Thus, according to some embodiments of the invention, the flammabletextile fabric having applied thereof the FR formulation presentedherein n is characterized by an amount of a binding agent which is lowerthan 25 weight percents of the total weight of the substrate, preferablylower than 20 weight percents of the total weight of the substrate, andmore preferably the amount of the binding agent ranges from 5 weightpercents to 20 weight percents of the total weight of the substrate.

These low amounts of binder allowed the textiles treated by theformulations presented herein to maintain their desirable textural andaesthetical properties, as well as their flame retardancy, as comparedto the untreated fabric.

In particular, it has been shown that textile substrates coated with theformulations described herein were characterized by feel and appearancesimilar to those of a non-treated fabrics. For example, properties suchas the flexibility, smoothness and streak-free look of a non-treatedtextile were maintained upon application of the FR formulation.Furthermore, these textural and aesthetical properties were maintainedalso upon subjecting the treated fabrics to several washing cycles.

Thus, according to some embodiments of the invention, there is provideda flammable textile fabric having an FR formulation as presented hereinapplied thereon, which is characterized by at least one aesthetical ortextural property which is substantially the same as that of saidflammable textile fabric per se.

The phrase “flammable textile fabric per se” as used hereinafter, refersto a flammable textile fabric which was not treated with the flameretardant formulation.

One particularly important aesthetical property is the transparency ofthe coating. As shown in the Examples which follow, the formulationspresented herein formed homogeneous and transparent coatings, forexample on glass, as described hereinabove. When applied on the fabric,these coatings effectively penetrated the fabric fibers, evenly coatingthem, with no agglomerates or non-melted particles being observedtherein. The transparency, smoothness and homogeneity of the coatingallowed the treated fabric to maintain its color, as can be seen in aseries of experiments measuring the CIE Lch color difference for avariety of colored fabrics treated by the formulations of the presentembodiments, compared to a similar white fabric (see, Examples 13-15).For example, a 100% black colored cotton twill treated by amilled-FR-720 formulation (see, Example 13, Table 7) had a relativelylow dE value (1.37), signaling only a minor color change. A blue colored50% cotton/50% polyester twill fabric treated by the same formulation(see, Example 14, Table 8) had a dE value of only 3.00, and a red brickcolored 100% acrylic plain weave fabric treated by this formulation(see, Example 15, Table 9) also had a low dE of 5.16.

The milled FR-720 formulations presented herein have proved to be highlyefficient in creating a uniform, homogeneous and transparent coating,which is both high in bromine and low in binder, and is therefore highlysuitable to be used not only on white and back-coated textiles, but alsoon colored textiles, for which the degree of transparency of the coatingis more critical.

Thus, according to some embodiments of the invention, the invention issuitable to treat a wide selection of fabrics, and is particularlysuitable to treat colored fabrics.

Furthermore, this treated flammable textile fabric is also characterizedby a relatively low amount of binder, since the applied formulationcontained less than 15% binder of the total weight of the formulation.

As is used herein, the term “flammable substrate” describes a substrate,as described hereinabove, that easily ignites when exposed to alow-energy flame. The flammability of different articles-of-manufacturecan be tested according to international standards. For example, theflame retardancy of the treated flammable substrates presented hereinwas determined by a 12 seconds ignition test, which is defined by ASTMD-6413, a test method used to measure the vertical flame resistance oftextiles. According to this method a textile is classified on apass/fail basis, according to predetermined criteria, usually of the“after-flame time”, “after-glow time” and “char length” of the testedsample.

An “after-flame time” is defined herein and in the art as the timeperiod during which the sample continues to burn after removal of theburner.

An “after-glow time” is defined herein and in the art as the time periodduring which the sample glows after the flame is extinguished.

A “char length” is defined herein and in the art as the distance fromthe edge of the fabric that was exposed to the flame to the end of thearea affected by the flame. A char is defined as a carbonaceous residueformed as the result of pyrolysis or incomplete combustion.

More specifically, a textile is considered to have failed the 12 secondsignition test, if its average “char length” exceeds 7 inches (17.8 cm)or an individual sample has a “char length” longer than 10 inches (25.4cm). The flammability of a substrate may be further defined by its“after flame time” and by its “after glow time”. A fabric is consideredto have an excellent flame retardancy if either its “after flame time”is 10 seconds or less, or its “after glow time”, is 200 seconds or less.A fabric is considered to have a superior flame retardancy if its “afterflame time” is 5 seconds or less.

Using this method, it was demonstrated, for example, that a bone-dry100% cotton knitted fabric, which was padded with a milled FR-720formulation (Example 11), according to preferred embodiments of thepresent invention, passed ASTM D-6413 12 seconds ignition test with anafter flame time of 2 seconds, an after glow time of 113 seconds, and achar length of 4.5 centimeters.

Similarly, a bone-dry 100% cotton knitted fabric, which was padded witha milled FR-720/AlASP aqueous formulation (Example 12), according tosome embodiments of the invention, passed ASTM D-6413 12 secondsignition test with an after flame time of 0 seconds, an after glow timeof 33 seconds, and a char length of 14 centimeters.

As defined hereinafter the term “bone-dry” describes a substrate havingzero percent moisture content.

The treated flammable textile fabrics described herein are thereforecharacterized by enhanced flame retardancy properties, which can bedetermined as described hereinabove.

Thus, the treated flammable textile fabrics according to the presentembodiments are characterized by an after flame time of 5 seconds andless; an after glow time of 150 seconds or less, preferably of 50seconds or less, and a char length of 15 centimeters or less, preferablyof 5 centimeters or less.

As is further demonstrated in the Examples section that follows, when anFR formulations as presented herein was applied onto various textilefabrics, the flame resistance of the fabric, as defined by the “afterflame time”, “after glow time” and “char length”, was obtained andmaintained even after the fabric was contacted with hot water and adetergent, while being subjected to several washing cycles, as definedby Standard Laboratory Practice for Home Laundering (AATCC technicalmanual/2001). In fact, the flame resistance properties of textilefabrics treated with the FR formulations described herein weremaintained even after the treated fabric was subjected to even 15washing cycles.

Hence, it has been shown that the treated textile fabrics arecharacterized by enhanced washing fastness and that the treatedflammable textile fabrics described herein have a durability of at least15 washing cycles.

The term “washing fastness”, which is also referred to hereininterchangeably as “washing durability” or “laundry stability”, refersto the ability of a substrate treated with the milled FR-720formulations of the present invention, to maintain its characteristicflame resistance and/or textural and/or aesthetical properties, afterbeing subjected to at least one washing cycle, as defined by StandardLaboratory Practice for Home Laundering (AATCC technical manual/2001).

As is well acceptable in the art, a textile is considered “durable” ifit withstands 5 washing cycles without having remarkable change of aproperty thereof. The substrates treated with the formulations of thepresent embodiments were characterized by a washing fastness of 15washing cycles. Hence, according to further embodiments of theinvention, the treated flammable textile fabrics described herein arecharacterized by washing fastness. This feature is particularly notablein view of the relatively low amount of the binder in the appliedformulation.

As discussed in the Background section hereinabove, textile flammabilityand textile smoldering are major concerns since textiles are used in allfields of life. Some textile-based articles of manufacture, such asgarments, linen and some decorative or technical textiles, are subjectto harsh usage (abrasion, exposure to various environmental conditionsetc.) and therefore may need extensive, sometimes daily, cleaning andwashing. Heretofore, fire proofing these articles of manufactureinvolved either using the few available non-flammable fabrics; coatingflammable fabrics with large amounts of FR, thus often damaging thefabric properties; or applying low amounts of FR on the flammablefabric, but limiting its cleaning method to the expensive and burdensomedry cleaning method. Using the FR formulation presented herein, thesegarments or technical textiles may be fire proofed while maintaining thefeel and look of the fabric, as a result of applying relatively smallamounts of the formulation.

Other types of flammable textile fabrics, such as draperies, carpets,tents, sleeping bags, toys, wall fabrics, decorative fabrics, mattressesand upholsteries, are not washed as much as garments or linen. However,the major hazards that can be caused by the inherent flammability ofthese articles call for efficient fire proofing thereof, in addition totheir durability during periodic cleaning. These articles of manufacturemay easily be made fire proof, either by using a fabric treated by theformulation described herein during the manufacturing process, or byeasily applying these formulations onto the final product.

As discussed in detail in the Background section above, commonly usedbrominated FRs are characterized by a high add-on, which then results ininferior textural and aesthetical properties.

As shown in the Examples section which follows, fabrics treated by theformulations presented herein were characterized by a combination of alow binder content and a high bromine content.

Thus, it has now been established that the milled FR-720 formulationspresented herein can serve as efficient and durable flame retardant andthat milled FR-720 particles can be incorporated in formulations thatare beneficially applied onto flammable substrates such as textilefabrics, while overcoming the limitations associated with the highbinder content of the presently known flame retardant formulations ofFR-720.

Additional objects, advantages, and novel features of the presentinvention will become apparent to one ordinarily skilled in the art uponexamination of the following examples, which are not intended to belimiting. Additionally, each of the various embodiments and aspects ofthe present invention as delineated hereinabove and as claimed in theclaims section below finds experimental support in the followingexamples.

EXAMPLES

Reference is now made to the following examples, which together with theabove descriptions, illustrate the invention in a non limiting fashion.

Materials and Analytical Methods

Materials:

Tetrabromobisphenol A bis(2,3-dibromopropyl ether) (CAS No. 21850-44-2)was obtained from Ameribrom Inc. as FR-720.

Antimony trioxide (ATO, CAS No. 1309-64-4) was obtained from Campine,Belgium.

Aluminum ammonium super phosphoric acid (AlASP) was prepared accordingto the procedure described in WO 07/096,883.

Ammonium hydroxide was obtained from Aldrich.

Triton X100® or TERGITOL™XD (a nonionic dispersing agent) was obtainedfrom DOW chemicals.

AC-200 W binder (a 45% solution) and acrylic thickening agent wereobtained from B. G. Polymers.

Instrumental Data:

Mixing was conducted using an IKEA lab mixer.

Viscosity was measured using a Bruckfield viscometer (model DV-E).

Size Distribution Tests:

Light scattering particle size measurement: This method was used todetermine the particle size distribution of liquid particles, using aMalvern Mastersizer (Hydrogel 2000G), manufactured by MalvernInstruments. The instrument uses the principle of MIE scattering, has anaccuracy of ±1%, and is set to measure particles in the size range0.02-2000 microns. A spherical (general) model was used. The surfacemean particle size (d₅₀) or 50 percentile, the 10 percentile (d₁₀) andthe 90 percentile (d₉₀) are directly obtained from the data generated bythe instrument.

Film Characterization Methods:

Film transparency was measured in two ways:

a) The interior walls of a glass turbimeter test bottle were coated by athin layer of a tested formulation, forming a film on the inside wall ofthe bottle. The bottle was then cured at 160° C. for 15 minutes, and theturbidity was measured in a Turb555 turbimeter WTW), using empty bottlesfor calibration.

b) Microscope slides were dip-coated by a tested formulation, forming afilm on the slide, which was then cured at 160° C. for 15 minutes. Thecured coated slides were then examined using a Nikon eclipse model ME600light microscope at ×75 or ×100 lens magnification.

Fabric Characterization Methods:

Scanning electron microscope (SEM) equipped with an energy dispersivex-ray spectrometer (EDS; hereinafter SEM/EDS) was performed on a JEOLJSM-7400F ultrahigh resolution cold FEG-SEM. In this method a piece offabric is coated with 10 nanometer of gold layer.

The percentage of bromine on the fabric was determined by addingtetrahydrofuran (THF) and extracting the coating from twelve fabricspecimens (referred to hereinafter as the “gridline-12-samples-test”)weighing 0.5 grams each (four specimens from the middle of the fabricand four from each the side of the fabric, as detailed below):

1 2 3 4 5 6 7 8 9 10 11 12

Each specimen is reacted with a sodium biphenyl complex reagent, toproduce NaBr in an amount equivalent to the amount of bromine in thesample. The access reagent is treated with isopropanol and acidifiedwith acetic acid. Finally, the amount of bromine is determined using atitration with AgNO₃.

The relative standard deviation (RSD) is a measure of thereproducibility of an analysis. This is determined by dividing thestandard deviation of a sample by the mean for the same set and thenmultiplying by 100. As defined herein, the term RSD refers to the RSDvalue of the bromine content, as obtained by the“gridline-12-samples-test” defined hereinabove.

The percentage of additives on the fabric (“Add-on”) was determined bythe difference between sample weight before and after application of theFR formulation (deviation of ±1%).

Fabric transparency was assessed by measuring the CIE color difference,using a Datacolor Spectraflash 650 (datacolor). The colors of bothtreated and non-treated fabrics were measured, using the CIE colorcoordinates, wherein:

-   -   L* indicates the lightness coordinate;    -   C* indicates chroma coordinate, the perpendicular distance from        the lightness axis (more distance being more chroma); and    -   h* indicates the hue angle, expressed in degrees.        The CIELAB color difference is then calculated as the difference        in each of the color coordinates:

DL* being the lightness difference.

DC* being the chroma difference.

Dh* being the hue angle difference.

DH* being the metric hue difference.

DE* being the color difference, and is calculated as

DE*=(DL ² +DC ² DH ²)^(1/2)

Flammability Tests:

ASTM D-6413 12 seconds ignition test: In this method, samples are cutfrom the fabric to be tested, and are mounted on a frame that hangsvertically from inside the flame chamber. The sample is exposed to acontrolled flame for a specified period of time (in this case for 12seconds, one of the strictest flammability tests), and the “after-flametime” and the “after-glow time” are both recorded. Finally, the sampleis torn by use of weights and the char length is measured. To pass, theaverage char length of five samples cannot exceed 7 inches (17.8 cm). Inaddition, none of the individual specimens can have a char length of 10inches (25.4 cm).

Washing Fastness Tests:

Samples treated with the flame retardant formulations described hereinwere subjected to 15 successive washing cycles in accordance with thewashing procedure set forth below, followed by one drying cycle inaccordance with commonly used drying procedure, based on the StandardLaboratory Practice for Home Laundering (AATCC technical manual/2001),unless otherwise noted.

In all washing cycles, the temperature of the washing water ismaintained between 58° C. and 62° C., for automatic washing machines,the washing cycle is set for normal washing cycle, and a syntheticdetergent that conforms to Standard Laboratory Practice for HomeLaundering (AATCC technical manual/2001) is used.

Example 1 Preparation of a Wet-Milled FR-720 Concentrate (Milling Base)

Tetrabromobisphenol-A bis(2,3-dibromopropyl ether) (labeled by themanufacturer as FR-720, 248 grams) was added in small portions to amixed solution of deionized water (241 grams) using a nonionicdispersing agent (TritonX100® 2% by weight) and the dispersion wasallowed to mix for 15 minutes. The size distribution of this coarsedispersion, characterized by a Malvern particle sizer, is presented inTable 1 below and in FIG. 1A. D₁₀, D₅₀ and D₉₀ of the dispersion beforemilling were 26 microns, 105 microns and 289 microns, respectively.

TABLE 1 Volume Volume Volume Size (μm) under (%) Size (μm) (%) Size (μm)(%) <2.188 0 26.303 10.27 316.228 91.47 2.512 0.03 30.200 11.83 363.07893.30 2.884 0.10 34.674 13.60 416.869 94.65 3.311 0.17 39.811 15.72478.630 95.69 3.802 0.27 45.709 18.32 549.541 96.52 4.365 0.39 52.48121.56 630.957 97.23 5.012 0.55 60.250 25.59 724.436 97.84 5.754 0.7769.183 30.47 831.764 98.39 6.607 1.07 79.433 36.20 954.993 98.86 7.5861.45 91.201 42.67 1096.478 99.25 8.710 1.94 104.713 49.65 1258.925 99.5510.000 2.56 120.226 56.84 1445.440 99.77 11.482 3.31 138.038 63.911659.587 99.91 13.183 4.20 158.489 70.54 1905.461 99.98 15.136 5.21181.970 76.49 2187.762 100 17.378 6.33 208.930 81.57 >2187.762 0 19.9537.55 239.883 85.73 22.909 8.86 275.423 89.00

Milling was conducted on an Agitator Bead Mill, Dyno®-Mill MULTILAB(manufactured by Wiley A. Bachofen (WAB)) using 0.3 millimeter(diameter) ceramic balls which filled about 65% of the milling vesselvolume, and running at medium speed (3-4 Kg/h). The milling canoptionally be conducted with ceramic balls of different diameter (forexample 1.5 millimeters, 2.5 millimeters etc.).

The coarse FR-720 dispersion was wet-milled at a rate of 3-4 kg/hour forabout 20 minutes, to obtain a smooth and uniform mill base, which istermed hereinafter a “concentrate”. The concentrate, containing about40% by weight solids, was non-gritty and homogeneous.

The size distribution of the obtained milled FR-720, characterized byMalvern particle sizer, is presented in Table 2 below and in FIG. 1B.D₁₀, D₅₀ and D₉₀ after milling were 3 microns, 14 microns and 38 micronsrespectively.

TABLE 2 Volume Size (μm) (%) <0.550 0 0.631 0.12 0.724 0.35 0.832 0.710.955 1.19 1.096 1.80 1.259 2.53 1.445 3.38 1.660 4.35 1.905 5.41 2.1886.57 2.512 7.81 2.884 9.13 3.311 10.53 3.802 12.04 4.365 13.73 5.01215.67 5.754 17.98 6.607 20.78 7.586 24.18 8.710 28.30 10.000 33.1711.482 38.80 13.183 45.08 15.136 51.84 17.378 58.82 19.953 65.74 22.90972.30 26.303 78.22 30.200 83.32 34.674 87.48 38.811 90.70 45.709 93.0552.481 94.69 60.256 95.76 69.183 96.46 79.433 96.92 91.201 97.25 104.71397.55 120.226 97.85 138.038 98.17 158.489 98.51 181.970 98.85 208.93099.17 239.883 99.45 275.423 99.67 316.228 99.85 363.078 99.94 416.86999.99 478.630 100.00 >478.630 0

Another sample, prepared by pooling several batches of coarse FR-720dispersions, and containing 37% solids, was wet milled as previouslydescribed. The viscosity of the dispersion was measured and wasdetermined to be in the range of 200-1,700 centipoises (cP), dependingon concentration. The size distribution of this second sample of milledFR-720 was also characterized by a Malvern particle sizer, wherein D₅,D₁₀, D₅₀, D₉₀ and D₉₅ after milling were 1.6 microns, 2.6 microns, 12.6microns, 39 microns and 69 microns respectively.

Optionally, in order to increase the stability of the concentrate and toavoid cake formation, a small amount of carboxymethylcellulose (CMC,0.5% by weight) was added to the concentrate. The obtained milledconcentrate dispersion was left on a shelf for 4 months and remainedstable (redispersion by simple mixing was easily achieved) during thisperiod.

Furthermore, in order to increase the solid content of the milledconcentrate from about 40% by weight to over 50%-55% by weight (so as tomake transportation more effective), decantation was performed on thepreviously obtained concentrate. Decantation can be avoided if the wetmilling is performed on a dispersion containing 50% solids (for example,under industrial conditions).

Example 2

General Protocol Preparation of Aqueous Formulations of Milled FR-720from a Milled FR-720 Concentrate

To prepare 1 kg of formulation, the FR-720 concentrate, preparedaccording to Example 1, is re-dispersed in water (5-500 grams), furtheradding additional components, such as antimony oxide (from 0 to 400grams and up to 1:3 Sb:Br molar ratio), acrylic binder (from 5 to 300grams), surface active agents (from 5 to 50 grams), antifoaming agents(from 5 to 50 grams), preservatives (from 5 to 50 grams), stabilizingagents (from 0 to 50 grams), thickening agents (from 0 to 100 grams),wetting agents (from 5 to 50 grams), suspending agents (from 5 to 50grams), pH buffers (from 5 to 100 grams) and any mixture thereof. Thecomposition is mixed for about 20 minutes, adding more deionized waterif necessary, to obtain a formulation having a viscosity in the range of100 to 5000 cps, suitable for application on a flammable substrate.Dispersing agents are usually added at the concentrate preparation stageand are therefore not required again at this stage; however, theirconcentration can reach 5-50 grams per 1 Kg formulation. Examples 3-6below represent specific formulations of the present invention, preparedaccording to this general procedure.

Example 3 A Homogenized Aqueous Formulation of 17.3% Milled FR-720, 15%Binder and ATO

An exemplary formulation containing 37.7% solids was prepared accordingto the general procedure of Example 2, by adding a mixed solution ofdeionized water (190 grams) and a Triton X100® dispersing agents (20grams) to the FR-720 concentrate (346 grams) prepared according toExample 1. Antimony oxide (73 grams) was added thereafter and thedispersion was allowed to mix for 15 minutes. An acrylic binder (AC-200W, 300 grams) was added during mixing and the dispersion was neutralizedto pH=8 using ammonium hydroxide (20 grams), further adding thickeningagent (50 grams), to obtain a formulation containing a total of 37.7%solids, as displayed in Table 3 below. The milled FR-720 whiteformulation was smooth, white and had good fluidity.

TABLE 3 Component Weight Percentage Dry solids 37.7 pH 8 FR-720 17.3 Br11.8 ATO 7.3 Binder 15.0 Sb:Br 1:3 (molar)

Example 4 Homogenized Aqueous Formulations of 27% Milled FR-720, 19%Binder and ATO

Another exemplary formulation, containing 58% solids, was prepared byrepeating the process of Example 3 while varying the amounts of FR-720,binder, ATO and water to obtain 27% FR-720, 19% binder and 12% ATO. Thesample contained 2% dispersant. This formulation appeared smooth, whiteand had good fluidity.

Example 5 Homogenized Aqueous Formulations Containing 27% Milled FR-720with No Binder and/or No ATO

Additional formulations according to the present embodiments wereprepared to assess the contribution of the binder and the ATO to theformulation properties, by omitting one or both ingredients (ATO and/orbinder) from the composition given in Example 3 (appearing asformulation 1 in Table 4 below), and adding deionized water to make upfor the missing weight. These formulations appear as numbers 2A, 3 and4A in Table 4 below.

Furthermore, in order to show the effect of the milling, formulations 2and 4 were prepared once more, substituting the milled FR-720 with anon-milled FR-720 (appearing as formulations 2B and 4B in Table 4below).

As another comparative experiment, formulations containing no FR-720 atall were also prepared: formulation 5 has only binder and formulation 6had binder and ATO, as appears in Table 4 below.

TABLE 4 FR-720 Binder ATO Deionized Water Formulation No.* (weightpercent) 1 27 19 12 42 (identical to formulation of Example 3) 2A 27 — —73 2B 27 — — 73 3 27 — 12 61 4A 27 19 — 54 4B 27 19 — 54 5 — 19 — 81 6 —19 12 69 * B-signifies FR-720 before milling; all other formulationswere prepared from milled FR-720.

Example 6 Homogenized Aqueous Formulations of 18.7% Milled FR-720, 15%Binder, 8.3% AlASP and Reduced Amounts of ATO

Another milled FR-720 aqueous formulation was prepared, according to theprocess of Example 2, further adding Aluminum Ammonium Super Phosphate(AlASP, 27-31 grams) to improve the after-glow suppression and to reducethe ATO requirement in the formulation to a Sb:Br molar ratio of 1:6.Other additives, such as softeners, thickeners, UV-absorbers,water-repellents etc. are added, depending on the applicativerequirements. The obtained FR-720 formulation was smooth, white and hadgood fluidity. Table 5 below details the composition of the FR-720/AlASPformulation:

TABLE 5 Component Weight Percentage Dry solids 40 pH 8 FR-720 18.7 Br12.6 AlASP 8.3 Sb₂O₃ 4.3 Binder 15.0 Sb:Br 1:6 (molar)

Example 7 General Protocol Preparation of Milled FR-720 Films andCoatings

Milled FR-720 dispersions, prepared according to Examples 1(concentrates) or 2-6 (formulations) above, are applied on a substrateby contacting (coating, dip-coating, spreading, padding, foaming and/orspraying) the substrate with the milled FR-720 dispersion. Then thesubstrate is cured at 140-180° C. (well above the melting temperature ofFR-720: 113-117° C.), for 3-15 minutes, depending on the substrate.Examples 8-15 below disclose the preparation of films and coatings ofpreferred embodiments, on glass (Example 8) and on textile fabric(Examples 9-15).

Example 8 Characterization of Milled FR-720 Films on Glass

The formulations prepared according to Examples 4 and 5 above wereapplied on the inside walls of glass turbidity test bottles, and onmicroscope slides, and their transparency was measured by turbimeter andusing a light microscope, respectively, being cured at 160° C. for 15minutes. The results are summarized in Table 6 below, wherein the filmnumbers correspond to the formulation numbers in Table 4. Film No. 1represents the film obtained according to preferred embodiments, from aformulation containing milled FR-720, binder and ATO. This film wasfound to have a turbidity of 105.91 NTU. Film No. 2A represents anotherfilm obtained according to preferred embodiments, from a formulationcontaining milled FR-720 only. This film was found to be highlytransparent, and had a turbidity of 9.41 NTU. Film No. 3 represents thefilm obtained according to preferred embodiments, from a formulationcontaining milled FR-720 and ATO (no binder). This film was found tohave a turbidity of 128.74 NTU, corresponding to a very homogeneousdispersion of ATO in FR-720, which blocked out light most efficiently.Film No. 4A represents the film obtained according to preferredembodiments, from a formulation containing milled FR-720 and binder (noATO). This film was found to have a turbidity of 55.29 NTU.

TABLE 6 Film description Film Acrylic Turbidity (slide under a No.FR-720 binder ATO [NTU] light microscope) 1 ✓ ✓ ✓ 105.91 ATO particles(visible as black spots) are almost homogenously dispersed (FIG. 2A)  2A✓ 9.41 Transparent film of a molten FR-720 formulation (FIG. 2B) 3 ✓ ✓128.74 ATO particles (visible as black spots) are homogenously dispersed(FIG. 2C)  4A ✓ ✓ 55.29 Melt drops are uniformly dispersed asdiscernible clusters in the acrylic film (FIG. 2D) 5 ✓ 4.83 transparentslide of a homogeneous acrylic binder film (FIG. 2E) 6 ✓ ✓ 107.54 ATOparticles (visible as black spots) are not homogenously dispersed in theacrylic film (FIG. 2F)

The comparative turbidimeter results show that the film prepared of anacrylic binder only (film no. 5) was as transparent as the film preparedof FR-720 only (film no. 2A). Furthermore, the film prepared from ATOdispersed in the acrylic binder (film no. 6) had a lower turbiditycompared to the ATO/FR-720 (film no. 3), only due to phase separationand a formation of large ATO clusters in the acrylic binder. Film No. 6was comparable in turbidity to film no. 1, signifying that the FR-720therein is indeed molten and fully transparent within the acrylic film.

Microscopic image analysis clearly indicates the differences in theappearance of the respective films. Pictures 2B and 2E, which representfilms prepared of FR-720 only (film no. 2A) and of an acrylic binderonly (film no. 5), respectively, both showed transparent and uniformfilms. Pictures 2C and 2F demonstrate that ATO was better dispersed inFR-720 melt (film no. 3, picture 2C) than in acrylic latex (film no. 6,picture 2F). This shows the advantage of FR-720 in better dispersing ATOin the formulations.

Example 9 Application of the Milled FR-720 Dispersions of Examples 3 and5 on a Woven Polyester Fabric

A polyester fabric weighing 164 grams per square meter was uniformlypadded with the milled FR-720 aqueous formulation, prepared as describedin Example 3 above, and cured at 160° C. for 4 minutes. The polyesterfabric was laundered to remove excess material on the surface. FIG. 3Apresents a SEM micrograph of polyester fibers treated with the milledFR-720 formulation, clearly illustrating the even distribution of thecoating on the fibers and the formation of a film of FR-720 on the fibersurface. In order to confirm the nature of the fiber coating, X-Rayelemental analysis of the SEM sample surface was conducted on theSEM/EDS device, confirming the bromine content in the material thatcovered the fibers and was between the fibers (see purple dots in FIG.3B).

Another polyester fabric sample was treated with a formulationcontaining only a dispersion of milled FR-720 (formulation 2A in Table 4above, Example 5) and cured at 160° C. for 4 minutes. The coatingappeared as melt on the fabric. SEM pictures of the sample are shown inFIGS. 4A-C. FIG. 4A (taken at a ×100 magnification) depicts the moltenFR-720 spread very homogenously on the fabric. FIGS. 4B and 4C presentthe appearance of the melt in higher magnifications (×200 and ×400,respectively). These figures further show that the melt smoothly andcompletely coats the fibers and is observed deep in the yarn core, andthat no significant clumps or inter yarn adhesions are observed.

Yet another polyester fabric sample was treated with a formulationcontaining a dispersion of milled FR-720 and an acrylic binder(formulation 4A in Table 4 above, Example 5). The coating containedparticles. SEM pictures of the sample before curing are shown in FIGS.5A-C. FIG. 5A (taken at a ×100 magnification) shows that the wholesample is evenly covered with the material. FIGS. 5B and 5C present theappearance of the melt in higher magnifications (×200 and ×400,respectively). These figures further show that the diameter of manyparticles is less than the fiber's diameter and there is goodpenetration to the yarns core. The coated polyester sample was thencured at 160° C. for 4 minutes. The coating appeared as a melt in film.SEM pictures of the sample are shown in FIGS. 6A-D. FIG. 6A (taken at a×100 magnification) presents the appearance of molten, milled FR-720with cured acrylic binder on the PET fabric and shows that the wholesample is covered with FR material as located by the back-scatteredelectron image. FIGS. 6B and 6C present the appearance of the melt inhigher magnifications (×200 and ×400, respectively). These figuresfurther show that the acrylic film uniformly coats the fibers and can bedetected in the yarn core. Little inter yarn adhesion or clumping isobserved. FIG. 6D presents a back-scattered electron image techniqueused on Picture 6B above, at ×400 magnification, conducted in order todetect the location of the FR-720 melt (bromine) under the acrylic film.This figure clearly shows that the flame retardant is present and spreadhomogenously on the fibers.

In another sample of cured polyester treated by the 4A formulation, theaverage bromine content on the fabric was determined to be 17.73%,having an RSD of the bromine content of ±11.5%.

Example 10 Comparative Application of Non-Milled FR-720 Dispersions on aWoven Polyester Fabric

In a comparative experiment, dispersions of the coarse (non-milled)FR-720, prepared as described in Example 1 above, were applied on apolyester fabric weighing 164 grams per square meter. The fabric wasair-dried and the formulation was then cured at 160° C. for 4 minutes.The add-on was determined to be 35%. The treated fabric passedFlammability Tests (ASTM D-6413-99) with negligible dripping. Althoughthere were no visible streak marks the fabric was merely translucent.

In additional comparative experiments, formulations 2B (containingnon-milled FR-720) and 4B (containing non-milled FR-720 and acrylicbinder) were similarly applied on a polyester fabric sample and cured at160° C. for 4 minutes.

Formulation 2B, containing non-milled FR-720 only, appeared as a meltedcoating on the fabric. SEM pictures of the sample are shown in FIGS.7A-C. FIG. 7A (taken at a ×100 magnification) depicts some particlesthat did not melt during the curing process, and a melt of big particles(agglomerates) appears to have formed a brittle film between the fibers.FIGS. 7B and 7C present the appearance of the melt in highermagnifications (×200 and ×400, respectively). These figures furthershow, in addition to clumps that partially melt during the curingprocess, that the melt was non-uniform and that it did not evenly coverthe fibers. Furthermore, inter yarn adhesions were observed.

Before curing of formulation 4B (containing a dispersion of a non-milledFR-720 and an acrylic binder) particles were present on the fabric. SEMpictures of the sample at this stage are shown in FIGS. 8A-C. Thesefigures show that the diameter of many particles was bigger than thefiber diameter and there was limited penetration to the yarns core. Thesample was then cured at 160° C. for 4 minutes, and a melt was apparenton the fabric. SEM pictures of the sample at this stage are shown inFIGS. 9A-D. FIG. 9A (taken at a ×100 magnification) presents theappearance of molten non-milled FR-720, with a cured acrylic binder onthe polyester fabric. Particles that did not melt during the curingprocess were observed, covered with acrylic film. FIGS. 9B and 9Cpresent the appearance of the melt in higher magnifications (×200 and×400, respectively). These figures further show that the acrylic filmthat coats the fibers was not smooth. A large quantity of material wasobserved between the yarns. FIG. 9D presents a back-scattered electronimage technique used on Picture 9B above, at X400 magnification,conducted in order to detect the location of the FR-720 melt (bromine)under the acrylic film. This figure clearly shows that the flameretardant was present only in inter yarn clumps inside the acrylic filmand was not spread homogenously on the fibers.

In another sample of cured polyester treated by the 4B formulation, theaverage bromine content on the fabric was determined to be 7.11%, havingan RSD of the bromine content of ±20%.

The results of the bromine content analysis express the difference inbromine absorption when applying non-milled versus milled FR-720 on thefabric. It is clear that at same conditions the amount of milled FR-720that absorbs on the fabric (equivalent to 17.73% bromine) is much higherthan the amount of the same FR, when applied in its non-milled form(equivalent to 7.11% bromine). Furthermore, the difference in brominedistribution throughout the fabric, as reflected in the RSD values,indicates a far more homogenous coating on the fabric when using amilled FR-720, as compared to non-milled FR-720 (RSD: 11.5%, RSD: 20.0%respectively). These results are consistent with the look and feel andappearance in micrographs of the fabric when using milled—versusnon-milled FR-720 coatings.

Example 11 Application of the Milled FR-720 Dispersions of Example 3 ona White 100% Knitted Cotton Fabric

A 100% cotton knitted fabric weighing 200 grams per square meter waspadded with the FR-720 aqueous formulation of Table 3, prepared asdescribed in Example 3 above. The formulation was smoothly applied onthe fabric and no grittiness or accumulation on the pad rollers wasobserved. The add-on was determined to be 30.8%, the FR content on thefabric being 14.2% (calculated to be equivalent to 9% bromine) and theATO content on the fabric was 6.0%. The treated fabric was laundered for15 washing cycles, after which it was cured at 105° C. for 30 minutes toachieve a “bone-dry” sample and passed an ASTM D 6413-99 12-secondsignition flammability test, having an after flame time of 2.0 seconds,an after glow time of 113 seconds, and a char length of 4.5 centimeters.The FR coating obtained on the fabric was transparent, with fabricfibers clearly visible under the film.

Formulation No. 2A (FR-720 only), prepared according to Example 4 above,was similarly padded on a 100% cotton knitted fabric of the samedensity, and the obtained coating was homogeneous, non-gritty andcompletely transparent.

Example 12 Application of Milled FR-720/AlASP Dispersion of Example 6 ona White 100% Knitted Cotton Fabric

A 100% cotton knitted fabric weighing 200 grams per square meter waspadded with the FR-720/AlASP aqueous formulation, prepared as describedin Example 6 above. The add-on was determined to be 30%, the FR contenton the fabric being 14.2% (equivalent to 9.6% bromine), the AlASPcontent on the fabric being 6.3% and the ATO content on the fabric being3.3%. The formulation was smoothly applied on the fabric and nogrittiness or accumulation on the pad rollers was observed. The fabrictreated with this formulation were laundered for 15 washing cycles,after which it was cured at 105° C. for 30 minutes to achieve a“bone-dry” sample and passed an ASTM D 6413-99 12-seconds ignitionflammability test, having an after flame time of 0 seconds, an afterglow time of 33 seconds, and a char length of 14 centimeters.

Example 13 Application of Milled FR-720 Dispersions on a Colored 100%Knitted Cotton Fabric

A 100% black colored cotton twill weighing 200 grams per square meterwas padded with the milled FR-720 aqueous formulations preparedaccording to Examples 4 and 5 above. The CIE Lch color difference wasmeasured using a spectrophotometer, compared to a similar white fabric,as displayed in Table 7 below (formulation numbers correspond to theformulation numbers in Table 4 above).

TABLE 7 Formulation FR- Acrylic No. 720 binder ATO dL dC dH dE 1 ✓ ✓ ✓8.56 1.57 −0.75 8.5 2A ✓ 1.36 −0.09 −0.13 1.37 3 ✓ ✓ 8.28 0.93 −0.608.35 4A ✓ ✓ 1.89 0.24 −0.28 1.93 5 ✓ 0.92 −0.13 −0.04 0.93 6 ✓ ✓ 9.430.90 −0.63 9.30

Table 7 shows a shift in Lightness (dL) together with a negligiblechange in chroma (dC) and/or hue (dH). Formulations 5 and 6 arecomparative examples and contain no FR-720: The pure acrylic film(formulation 5) was used as a reference for a transparent coating,showing the least effect on fabric appearance (low dE 0.93) indicatinghigh transparency and the least change in refractive index compared toair. On the other side of the scale, the acrylic and ATO film(formulation 6) was used as a reference for an opaque coating, showingthe highest effect on fabric appearance (high dE, 9.30), and indicatingATO's critical effect on appearance.

Formulation 2A (FR-720) and Formulation 4A (FR-720+acrylic binder) werecharacterized by relatively low dE values (1.37 and 1.93, respectively).The formulations containing ATO (formulations 1 and 3) had higher colorshifts, proving the effective dispersion of the ATO particles within theFR-720 and binder particles.

Example 14 Application of Milled FR-720 Dispersions on a Colored 50%Cotton/50% Polyester Twill Fabric

A blue colored 50% cotton/50% polyester twill fabric, weighing 200 gramsper square, was padded with the milled FR-720 aqueous formulations,prepared according to Examples 4 and 5 above. The CIE Lch colordifference, compared to a similar white fabric, as displayed in Table 8below (formulation numbers correspond to the formulation numbers inTable 4 above). Formulations 5 and 6 are comparative examples andcontain no FR-720.

TABLE 8 Formulation FR- Acrylic No 720 binder ATO dL dC dH dE 1 ✓ ✓ ✓6.32 −3.87 −1.24 7.51 2A ✓ −0.40 −2.92 0.55 3.00 3 ✓ ✓ 8.03 −4.01 −2.399.29 4A ✓ ✓ −0.58 −2.56 −1.00 2.81 5 ✓ −1.15 −2.04 1.06 2.57 6 ✓ ✓ 3.82−2.09 −0.54 4.39

Table 8 shows larger changes in the chroma (dC) as a result of an easierpenetration of the hydrophobic FR-720 into synthetic fibers, as is alsoillustrated in FIGS. 3A and 3B. Again, the pure acrylic film(formulation 5) had the least effect on fabric appearance, followed byformulation 2A (FR-720) and formulation 4 (FR-720+acrylic binder), andfinally with the formulations containing ATO (formulations 1, 3 and 6).Again, the color shift of formulation 1 proves the effective dispersionof the ATO particles within the FR-720 and binder particles.

Example 15 Application of Milled FR-720 Dispersions on a Colored 100%Acrylic Plain Weave Fabric

A red brick colored 100% acrylic plain weave fabric, weighing 140 gramsper square meter, was padded with the FR-720 aqueous formulationsprepared as described in Example 3 above. The CIE Lch color difference,compared to a similar white fabric, is displayed in Table 9 below(formulation numbers correspond to the formulation numbers in Table 4above). Formulations 5 and 6 are comparative examples and contain noFR-720.

TABLE 9 Formulation FR- Acrylic No 720 binder ATO dL dC dH dE 1 ✓ ✓ ✓3.47 −5.86 −2.24 7.17 2A ✓ −1.88 −4.60 −1.42 5.16 3 ✓ ✓ 4.65 −6.34 −2.258.16 4A ✓ ✓ −0.9 −4.21 −1.47 4.55 5 ✓ −0.32 −0.24 −0.36 0.54 6 ✓ ✓ 3.27−4.91 −2.03 6.24

Table 9 also shows a large change in chroma (dC) as a result of aneasier penetration of the hydrophobic FR-720 into the acrylic syntheticfiber, as is also illustrated in FIGS. 3A and 3B. This fabric shows thesame pattern of the pure acrylic film (formulation 5) having the leasteffect on fabric appearance, followed by the FR-720 formulation (no. 2),the FR-720 and acrylic binder (no. 4), and finally the formulationscontaining ATO (formulations 1, 3 and 6). As in the previous coloredfabrics, the color shift of formulation 1 proves the effectivedispersion of the ATO particles within the FR-720 and binder particles.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting.

1. A flame retardant formulation comprising tetrabromobisphenol Abis(2,3-dibromopropyl ether) (FR-720) particles in a liquid carrier,wherein the particle size of at least 50% of said particles (d₅₀) issmaller than about 50 microns.
 2. The formulation of claim 1, furthercomprising a dispersing agent.
 3. The formulation of claim 1, furthercomprising a binding agent, wherein an amount of said binding agent isless than 25 weight percentages of the total weight of the formulation.4. The formulation of claim 3, wherein said amount of said binding agentranges from 5 weight percentages to 20 weight percentages of the totalweight of the formulation.
 5. The formulation of claim 1, wherein theparticle size of at least 90% of said particles (d₉₀) is smaller thanabout 100 microns.
 6. The formulation of claim 1, wherein the particlesize of at least 10% of said particles (d₁₀) is smaller than about 10microns.
 7. (canceled)
 8. The formulation of claim 1, further comprisinga smoldering suppressant agent.
 9. The formulation of claim 8, whereinsaid smoldering suppressant agent is an aluminum complex of ammoniumsuperphosphoric acid (AlASP).
 10. The formulation of claim 8, wherein aratio between said smoldering suppressing agent and said FR-720particles ranges from about 1:5 and 5:1.
 11. The formulation of claim10, wherein said ratio ranges from about 1:1 and 1:3.
 12. Theformulation of claim 1, further comprising a flame retardant synergist.13. The formulation of claim 12, wherein the formulation comprises AlASPand the synergist is antimony oxide (ATO).
 14. The formulation of claim13, wherein a molar ratio between an elemental antimony in said ATO andan elemental halogen in said FR-720 is less than 1:3.
 15. Theformulation of claim 1, wherein said liquid carrier is an aqueouscarrier.
 16. The formulation of claim 15, being in a form of an aqueousdispersion.
 17. The formulation of claim 16, wherein said particles arehomogeneously dispersed in said dispersion.
 18. The formulation of claim1, comprising FR-720 in an amount of between 5 weight percents to about70 weight percents, an acrylic binder in an amount of between 5 weightpercents to about 50 weight percents, antimony oxide in an amount of upto about 40 weight percents, and water.
 19. The formulation of claim 18,further comprising AlASP in an amount of up to 70 weight percents. 20.The formulation of claim 1, being characterized by a viscosity thatranges from about 100 centipoises to about 2000 centipoises.
 21. Aflammable textile fabric, being coated by a flame retardant film,wherein said film comprises tetrabromobisphenol A bis(2,3-dibromopropylether) (FR-720) particles which are substantially homogeneouslydispersed in or on said treated flammable textile fabric.
 22. (canceled)23. The flammable textile fabric of claim 21, being characterized by atleast one aesthetical or textural property which is substantially thesame as that of said flammable textile fabric per se.
 24. The flammabletextile fabric of claim 21, being a colored textile fabric.
 25. Theflammable textile fabric of claim 21, having a durability of at least 15washing cycles.
 26. The flammable textile fabric of claim 21,characterized by a relative standard deviation (RSD) of average brominecontent, as defined by a gridline-12-samples-test, which is smaller than15%, wherein said average bromine content is calculated upon cuttingsaid fabric into twelve equal slices each weighing about 0.5 grams,separately measuring the bromine content of each slice, and calculatingthe RSD of said separate bromine content values.
 27. The flammabletextile fabric of claim 21, characterized by an after flame time, asdefined by ASTM D-6413 12 seconds ignition test, of less than 5 seconds.28. The flammable textile fabric of claim 21, characterized by an afterglow time, as defined by ASTM D-6413 12 seconds ignition test, of lessthan 150 seconds.
 29. The flammable textile fabric of claim 28,characterized by an after glow time, as defined by ASTM D-6413 12seconds ignition test, of less than 50 seconds
 30. The flammable textilefabric of claim 21, characterized by a char length, as defined by ASTMD-6413 12 seconds ignition test, of less than 15 centimeters.
 31. Theflammable textile fabric of claim 30, characterized by a char length, asdefined by ASTM D-6413 12 seconds ignition test, of less than 5centimeters.
 32. A process of preparing the flame retardant formulationof claim 15, the process comprising: mixing tetrabromobisphenol Abis(2,3-dibromopropyl ether) (FR-720) particles having a d₅₀ that islarger than 50 microns, with an aqueous carrier, and milling saiddispersion until: a) the particle size of at least 90% of said FR-720particles (d₉₀) is smaller than about 100 microns; and/or b) theparticle size of at least 50% of said FR-720 particles (d₅₀) is smallerthan about 50 microns; and/or c) the particle size of at least 10% ofsaid FR-720 particles (d₁₀) is smaller than about 10 microns.
 33. Theprocess of claim 32, wherein said milling is conducted for at least 10minutes.
 34. (canceled)
 35. A process of applying the flame retardantformulation of claim 1 onto a flammable textile fabric, the processcomprising: Contacting the flammable textile fabric with the flameretardant formulation of claim 1, to thereby obtain a flammable textilefabric having said formulation applied thereof; and heating said treatedflammable textile fabric. 36-37. (canceled)